Mixed brain pathologies account for most dementia cases in community-dwelling older persons. Careful neuropathological studies have shown that aggregations of -syn, A and tau appear in the same neuronal structures, providing a pathological basis for the clinical observations of the overlap between PD/DLB and AD. Studies with transgenic (Tg) mice with neuronal expression of human A and -syn the doubly Tg mice resembled the Lewy-body variant of Alzheimer's disease (39). These mice had severe deficits in learning and memory, developed motor deficits before -syn Tg mice, and showed prominent age- dependent neurodegeneration. More recently, mutant (A53T) -syn Tg mice were crossed onto 3xTg-AD Tg mice (DLB-AD mice). The DLB-AD mice exhibit accelerated cognitive decline associated with a dramatic enhancement of A, tau, and -syn pathologies (40). Thus approaches that promote the clearance of -syn may provide therapeutic benefit for PD and DLB, as well as AD. Two studies have now shown that active and passive anti--syn immunotherapy can decreased aggregated -syn in neuronal cell bodies and synapses and improve behavior (1, 2). In this competitive renewal the goals are to design multi-epitope anti--syn DNA vaccines and test their therapeutic potential in Tg models that develop human-like neuronal -syn pathology and mixed pathology. To fully achieve these goals we propose the following 4 Aims: Aim 1: Fine mapping of the B-cell and T-cell epitope(s) of -syn in response to DNA Immunization. We will analyze the B- and T- cell immune responses to anti--syn DNA Immunization in wild-type mice. Mice will be vaccinated with DNA encoding full-length human -syn protein. Anti- -syn titers and the B-cell and T-cell epitopes will be identified. Aim 2: Testig of candidate multiple-epitope DNA vaccines in wild-type mice. A multi-epitope design where -syn B-cell epitopes (12, 15, 52, 54) will be fused with PADRE and as the foreign T helper cell epitopes. Both antibody titers and affinity will be measured. Aim 3. Testing prophylactic and therapeutic efficacy of -syn DNA epitope vaccines Tg mice. Human wild-type -syn (hSYN line D) mice (3) will be used. We will assess the ability of the best multi-epitope vaccines to induce protective immune response in pre-pathology 2 months old hSYN Tg mice, and therapeutic response to pre-existing a-syn pathology in 6 months old hSYN Tg mice. Aim 4. Testing the efficacy of -syn DNA epitope vaccine(s) in mixed pathology Tg mice. We will test the ability of the best multi-epitope -syn DNA vaccine to induce protective immune response in pre-pathology 2 months old mixed pathology DLB-AD Tg mice. The DLB-AD mice exhibit accelerated cognitive decline associated with a dramatic enhancement of A, tau, and -syn pathologies. Immunized DLB-AD Tg mice will be compared against non-immunized mice for cognitive decline and A, tau, and -syn pathologies. Finally, we will compare the best multi-epitope -syn DNA vaccine against our best multi-epitope A DNA vaccine in the mixed pathology DLB-AD Tg mice (40).